A major problen in the poultry industry is the high incidence of infectious diseases which increase the cull rate and also cause a high rate of mortality during the growing stage of the young birds. It has thus become standard practice in commercial hatchery operations to immunize the birds against such diseases. The most widely used method of accomplishing this immunization is to manually inoculate (by injection of a suitable antibiotic) each individual bird after it has been hatched. Since a skilled operator can manually inject only approximately 800 young birds per hour, the operation is relatively expensive.
Another method of inoculation which has become quite popular, particularly in turkey hatcheries, is egg dipping, whereby a temperature differential or vacuum is used to force the antibiotic solution through the shell of the embryonated egg. This method has the advantage of lower labor costs than manual inoculation; however, because of varying shell porosity and thickness, the amount of solution absorbed by the egg varies dramatically. A test of 6,174 dipped eggs revealed that 18% of the eggs took in essentially no solution at all and an additional 36% took in too little solution to be effective. From this test, it was concluded that dipping cannot stop the perpetuation of disease and even encourages the development of organisms resistant to these few antibiotics which are now effective.
Solution cost is also a detrimental factor in dipping. Most antibiotics are quite expensive with some costing over $64.00 per gallon. Approximately 24 gallons of dipping solution are consumed for every 100,000 eggs dipped. This is 1.06 ml per egg and is 5 to 10 times the average amount of solution that actually enters the egg.
Because of the high solution cost and uncertainties associated with dipping, few chick hatcheries dip eggs and almost all hatcheries that do dip eggs (primarily turkey hatcheries) also manually inoculate the day old birds.
One other method of inoculation involves the use of a hypodermic needle to inject the antibiotic solution into the egg. Egg injection is the only method known today that can introduce a precise and known quantity of solution into the egg. Day old birds that come from eggs injected prior to incubation all retain a sufficient amount of antibiotic, bactericide, vitamins or the like so that there is no need to manually inoculate the hatched bird. However, until the development of the invention described herein, the costs associated with egg injection made it impractical.
There are 3 major factors to be concerned with regarding egg injection. First, the region of the shell that is to be pierced must be sterile so there is no possibility of bacteria entering the egg during puncture. Second, the hole in the egg shell must be effectively sealed after injection to keep albumin from draining out and to keep bacteria from entering the egg. Third, the needle must be sterilized between injections; otherwise the possibility exists of transfer of bacteria from an infected egg to other eggs.
The use of a sharp pointed hypodermic needle to pierce a hole through the shell is often impractical for two reasons. First, the point on the needle rapidly becomes dull after only a few shells have been punctured. Second, the wedge-like action of the needle point causes the shell to fragment and the region around the hole to check and crack. A dental drill can be used effectively to drill a hole in the shell, and this technique has been used commercially, the drilling operation being followed by inserting a hypodermic needle through the drilled hole. After the antibiotic has been injected the hole is sealed with a cement. It is estimated that eight operators can manually inject 25,000 eggs per day by this method.
The present invention provides an automatic egg injection system which permits a much higher rate of egg treatment. It is estimated that with this system one trained operator can inject over 100,000 eggs per day.
One feature of the invention that makes high production rates possible is the use of heat to sterilize the surface of the egg prior to puncture of the shell. In the preferred embodiment this is accomplished by a heating element that contacts the surface of the egg at the point the puncture is to be made. An area on the surface typically 3/16 inch in diameter is heated rapidly to typically 180.degree. - 220.degree. F. to kill surface bacteria.
Another feature of the invention is the use of heat to seal the hole in the shell after injection. In the preferred embodiment, after the antibiotic solution has been injected through a hole in the egg, a heating element is brought in contact with the egg at the point of puncture. Temperature is increased to typically 500.degree. - 650.degree. F. for a brief period, typically about 2 seconds resulting in coagulation or cooking of the albumin in and just around the hole. The coagulated albumin acts as an effective sealant and blocks the entrance of any bacteria through the hole. The coagulated albumin also seals any checks or cracks that might have occurred during formation of the hole.
A further feature of this invention is the use of heat to sterilize the hypodermic needle between injections. After injection, the portion of the needle that penetrates the egg is withdrawn into a heating element. The portion of the needle that was inside the egg is heated to a temperature sufficient to kill any bacteria that might cling to the needle upon withdrawal from the egg.
A further feature of the invention is to form the hole in the shell with a cylindrical cutter having a squared-off or flat penetrating end which acts as a cutting die. The end of the special cutter is placed in contact with the egg, and the cutter is then given a sharp impact blow that drives it through the egg shell. This action, resulting from engagement of the entire circumference of the cutter with the shell at one time, causes a small circular disc the same diameter as the cutter to be sheared away from the shell. That is, the hole in the shell is the result of a "stamping" action that stamps out a circular piece of shell. The edge of the hole is clean and smooth. There is no fragmentation, nor are there any checks or cracks around the hole. Preferably the cutter is the hollow needle itself.
The squared-off or flat-ended needle may have an axial injection hole at its injection end, but preferably the end is closed and one or more radial injection holes are provided. The radial hole causes the antibiotic to be injected sideways into the albumin so as to avoid direct engagement with the yoke and embryo. In a high volume automatic production apparatus, such as is described in this invention, the antibiotic must be injected rapidly. Thus, the solution may enter the egg with considerable pressure. If this solution is injected straight into the egg through an end hole in the needle, there is considerable risk of the antibiotic directly contacting and damaging the embryo.
Another feature of this invention is the injection of solutions of one or more selected antibiotics, bactericides, vaccines, beneficiating chemicals, vitamins or the like into embryonated eggs using (1) heat sterilization of the egg surface and/or (2) a needle having a squared-off end to pierce the egg shell and/or (3) heat coagulation of the egg albumin to seal the pierced hole after injection and/or heat sterilization of the injection needle after injection and withdrawal from the egg. Specific examples of materials which may be injected are as follows: Garasol (Gentamicin sulfate), Tylusin, Encephalomyelitis Vaccine, Bronchitis Vaccine, Coccidiosis Vaccine, Erysipelas Vaccine, Fowl Cholera Vaccine, Fowl Coryza Vaccine, Fowl Pox Vaccine, Gumboro Vaccine, Laryngotracheitis Vaccine, Marek's Disease Vaccine, Newcastle Vaccine, Pigeon Pox Vaccine, Thiamine, Pyridoxine, Pontothenic Acid, Ribioflabin, Folic Acid, Niacin, Choline, Biotin, Vitamin B-12, Vitamin A, Vitamin D, Vitamin E, and Vitamin K.